EXPLOSIVE STRESS REACTION
For most animals, stress is a turn-off – but not for male spotted salamanders.
The dotted amphibians are explosive breeders, gathering together en masse for a brief period during which males deposit packages of sperm for collection by females.
New research shows that males respond to danger – in this case, human handling – by depositing more sperm when they next meet a female.
While other animals would postpone reproduction until the threat has passed, salamanders have evolved to consider they may not get another chance – and should go out with a bang. The club-like claws of the mantis shrimp are great for smashing open crabs, but something of a liability in contests with rivals. Little surprise, then, that they prefer alternative methods.
In the Central American species Neogonodactylus bredini males attempt to settle contests quickly and bloodlessly, displaying their open claws to intimidate competitors. This doesn’t work, though, when the opponents are similar sizes. In that case, they escalate to sparring, absorbing blows with their tail-plates. The winner is the one who can deliver the most strikes, rather than the hardest.
If they are still evenly matched, things get grisly. According to Patrick Green of Duke University, Durham, North Carolina, their clubs aren’t their only weapons: “When contests escalated past sparring, we saw competitors unfold part of their claw and use it to spear each other.” The two terms are often used interchangeably to describe an organism that deploys toxins for the purposes of attack or defence. Biologically, though, they have specific meanings. Venomous species such as jellyfish, black widows and adders actively deliver their chemical arsenal into their victim with a bite or sting. But poisonous ones – for example ladybirds, poisonarrow frogs and yew berries – are more passive, and only unleash their toxins when nibbled or touched. However, eat a venomous animal and you could find it proves to be poisonous, too.
Adders are venomous as they deliver toxin through a bite.